The utility of standoff detection of molecules has been demonstrated in the solid and gas phase, for example methane in field experiments and in the detection of explosive dust collected on solid surfaces. However, many chemical processes occur in solution phase, and involve a number of different molecules with similar functional groups. Vibrational spectra of species in solution can be interpreted to give thermal energies of IR-active compounds, allowing these to be included in chemical kinetic and dynamical models. In aqueous solution, there are two issues that need to be addressed, the high background and spectral selectivity. Hence, Raman is usually the method of choice for vibrational spectroscopy as it avoids background absorption from H2O. Because of selection rules, Raman is generally much less sensitive than IR absorption, unless methods such as surface enhanced Raman are used. Raman has been used to monitor the degradation of anion-exchange resins used for the separation of plutonium isotopes in highly acidic conditions. Because this method depends on far UV excitation; however, this method becomes unfeasible for use in applications involving high concentrations of nitrate because self absorption becomes problematic at concentrations above 3.5 mM. The detection limit for such methods have been reported at concentrations range of few milligrams per liter.